During the completion of a well that traverses a hydrocarbon bearing subterranean formation, production tubing and various completion equipment are installed in the well to enable safe and efficient production of the formation fluids. For example, to control the flowrate of production fluids into the production tubing, it is common practice to install a fluid flow control system within the tubing string including one or more inflow control devices such as flow tubes, nozzles, labyrinths or other tortuous path devices. Typically, the production flowrate through these inflow control devices is fixed prior to installation based upon the design thereof.
It has been found, however, that due to changes in formation pressure and changes in formation fluid composition over the life of the well, it may be desirable to adjust the flow control characteristics of the inflow control devices and, in particular, it may be desirable to adjust the flow control characteristics without the requirement for well intervention. In addition, for certain completions, such as long horizontal completions having numerous production intervals, it may be desirable to independently control the inflow of production fluids into each of the production intervals.
Attempts have been made to achieve these results through the use of autonomous inflow control devices. For example, certain autonomous inflow control devices include one or more valve elements that are fully open responsive to the flow of a desired fluid, such as oil, but restrict production responsive to the flow of an undesired fluid, such as water or gas. It has been found, however, that systems incorporating current autonomous inflow control devices suffer from one or more of the following limitations: fatigue failure of biasing devices; failure of intricate components or complex structures; lack of sensitivity to minor fluid property differences, such as light oil viscosity versus water viscosity; and/or the inability to highly restrict or shut off unwanted fluid flow due to requiring substantial flow or requiring flow through a main flow path in order to operate.
Accordingly, a need has arisen for a downhole fluid flow control system that is operable to independently control the inflow of production fluids from multiple production intervals without the requirement for well intervention as the composition of the fluids produced into specific intervals changes over time. A need has also arisen for such a downhole fluid flow control system that does not require the use of biasing devices, intricate components or complex structures. In addition, a need has arisen for such a downhole fluid flow control system that has the sensitivity to operate responsive to minor fluid property differences. Further, a need has arisen for such a downhole fluid flow control system that is operable to highly restrict or shut off the production of unwanted fluid flow though the main flow path.